JPS6140967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an erecting zoom telephoto optical system for binoculars or monoculars, which has an objective lens system, an eyepiece lens system, and an erecting prism for erecting an image.

A telescope configured such that a spatial image formed by an objective lens system is observed by an eyepiece system is known as a Kepler type telescope, and binoculars or monoculars having this structure have been used for a long time. Binoculars consist of two parallel optical systems, and the two optical systems are equivalent to each other except for diopter correction for the left and right eyes.
That is, since monoculars consist of only one of these structures, binoculars will be described below as a representative example.

Various types of zoom binoculars are known in which the magnification can be continuously changed. First, the so-called eyepiece zoom, which is based on a method of changing the magnification of an eyepiece lens system, can have a relatively simple configuration because the eyepiece lens itself has a small aperture. However, with this method, the magnification is changed within the eyepiece system, which has a short focal length, so it is possible to maintain a wide field of view while maintaining the eye relief (the distance from the light exit side of the eyepiece to the eyepoint) at a predetermined length. It is extremely difficult to properly correct aberrations across the field, and as a result, one has no choice but to settle for a narrow field of view. Furthermore, since the field aperture is generally fixed, the apparent field of view changes. In particular, in medium-sized eyepiece zooms (so-called eyepiece objective zooms) in which a spatial image is formed by the objective lens inside the eyepiece, the lens that holds the field diaphragm moves, so the image moves relative to the fixed diaphragm. It cannot fully fulfill its role as an aperture. This problem can be solved by arranging the aperture to move in conjunction with the movement of the lens when changing the magnification, and by changing the aperture of the aperture, but this becomes extremely complicated.

On the other hand, a system in which the magnification is varied using an objective lens, that is, a so-called objective zoom, has been considered, but since the magnification is varied by an objective lens having a large aperture, the overall shape is extremely large and the structure is complicated. In order to make the zoom system of the objective lens compact, the refractive power of each lens must be strengthened, which inevitably causes significant aberrations, making it impossible to obtain compact zoom binoculars that can withstand practical use.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned drawbacks and to provide an erecting zoom telephoto optical system which has a simple construction, a compact shape, and excellent performance.

The zoom optical system according to the present invention basically belongs to a so-called objective zoom, and its configuration is such that the single magnification of a variator group with negative refractive power that moves on the optical axis for variable magnification becomes positive. A compensator group is provided which forms an object image at a predetermined position by interlocking with this variator group, and between this compensator group and the above-mentioned variator group, a This is an arrangement of erect prisms.

The basic configuration of the present invention will be explained in detail below with reference to the drawings. The objective lens system _L1 includes a focusing group _L11 that has positive refractive power and moves on the optical axis according to the object distance, a variator group _L12 that has negative refractive power, and a compensator that has positive refractive power. further comprising _a variator group L ₁₂
An erecting prism P is arranged between the compensator group L13 and the compensator group _L13 . The variator group L ₁₂ and the compensator group L ₁₃ can be moved in conjunction with each other on the optical axis, and as a result of these movements, an object image is formed at the fixed position of the field stop S with continuously changing magnification. Ru. This object image is created using the eyepiece lens system.
Magnified observation through L ₂ .

The erecting prism, which is essential in binoculars, generally requires a fairly long optical path length, but in the configuration of the present invention, in order to arrange the erecting prism between the variator group L ₁₂ and the compensator group L ₁₃ , The gap between both groups is made quite large, and the negative refractive power of the variator group _L12 is made quite small.
That is, the absolute value of the refractive power of the variator group _L12 is smaller than that of the focusing group _L11 . Specifically, the individual magnification of the variator group L ₁₂ is positive, that is, when the distance to the apparent object point O ₁ of this group is a, and the distance to the apparent image point O' ₁ is b, then b /a is configured to be positive. With only a single negative lens as this variator group, it is also possible to satisfactorily correct various aberrations over the entire zoom range. Furthermore, since the refractive power of the variator group is negative, the focusing group and the variator group can be made teletype and can be shortened, and the aperture of the erecting prism can also be made relatively small, which is advantageous for making the overall shape more compact. Become.

Further, here, the erecting prism P may be fixed with respect to the spatial image I, or may be mechanically provided so as to be movable integrally with either the variator group L ₁₂ or the compensator group L ₁₃ . You can also do it.
The prism shown in the figure, which is used as an erecting prism, has a substantial diaphragm function, so when the prism is moved together with the lens that moves when changing the magnification, the distance between the two must be appropriately selected. In particular, it is also possible to configure the exit pupil diameter to be kept constant even when the magnification is changed.

According to the erecting type zoom telephoto optical system of the present invention as described above, the erecting prism is arranged between the variator group and the compensator group and the air gap is effectively utilized, so the overall shape is small. In addition, zoom binoculars with excellent performance can be realized even though the configuration of each group is extremely simple. Furthermore, since the same eyepiece lens as fixed magnification binoculars is sufficient, a wide apparent field of view can be obtained with a simple configuration.
Since the aerial image is formed at a fixed position, a fixed field stop can be placed.

In addition, in the above explanation, the objective lens system is
Although a group configuration is used, it is of course possible to use a four-group configuration. Furthermore, in order to better correct various aberrations, it is also possible to configure each group with a plurality of lenses. Even if the configuration of each group becomes complicated, an erecting prism may be placed between a lens that primarily functions as a variator and a lens that primarily functions as a compensator, and both are within the scope of the present invention. It is included. In addition, various types of erecting prisms are known, such as roof prisms and Porro prisms, but in the present invention, since the lenses that sandwich the prism move, the optical axes of the prism's light flux entrance surface and exit surface are on the same straight line. It is desirable to use a roof prism or the like. According to such a prism, the mechanism for moving the lens group is simpler, easier to manufacture, and performance is improved.

Furthermore, focusing was performed by moving the positive lens _L11 located closest to the object on the optical axis, but this positive lens _L11 was fixed, and the field diaphragm and eyepiece system _L2 were fixed. It is also possible to move them together on the optical axis.

[Brief explanation of the drawing]

The drawing is a layout diagram of the erecting type zoom telephoto optical system of the present invention. [Explanation of symbols of main parts], L ₁ ... Objective lens system, L ₁₁ ... Focusing group, L ₁₂ ... Variator group, L ₁₃ ... Compensator group, P ... Erecting prism, S ... Field of view Aperture, I...object image,
L ₂ ...eyepiece system.

Claims (1)

[Scope of Claims] 1. A positive lens system facing the object, an erecting prism disposed behind the positive lens system, a field stop and an eyepiece system disposed behind the erecting prism,
In the erecting telephoto optical system, a variator group with negative refractive power is provided between the positive lens system and the erecting prism, and a compensator group is provided between the erecting prism and the field stop. . An upright zoom telephoto optical system, characterized in that the individual magnification of the variator group is set to be positive. 2. The erecting type zoom telephoto optical system according to claim 1, wherein the erecting prism moves integrally with either the variator group or the compensator group. 3. Focusing is performed by moving the positive lens system on the optical axis or by moving the field stop and the eyepiece system together on the optical axis. The upright zoom telephoto optical system described in .